1. Field of the Invention
This invention relates to a method of controlling copying-paper feed in an image forming apparatus, and more particularly, to a method of controlling an image forming apparatus having, for example, an original feeder.
2. Description of the Related Art
A conventional image forming apparatus having an original feeder will now be explained by reference to FIGS. 1-13.
In FIGS. 1-13, there is shown a main body 1 of the copier, a recycling original feeder 2 (termed hereinafter an "ROF"), a sorter 3 (termed hereinafter a "stapler/sorter") having a stapler 5, and a large-capacity accumulation tray 4 (termed hereinafter a "paper deck").
When the user intends to have m copies of an original composed of n pages followed by sorting and stapling using this apparatus, he places the original O on a tray 11 of the ROF 2, selects a staple/sort mode, sets the number m of copies, presses a copy button (not shown) on the main body 1 of the copier. As shown in FIG. 2, the ROF 2 rotates a paper supply roller 12, a feed roller 13 and a separation belt 14 in the directions of arrows "a", "b" and "c", respectively, and first feeds the bottom sheet of the original O as shown in FIG. 3. As shown in FIG. 4, after the front end of the sheet of the original O has been detected by a sensor 16, the sheet is fed while stopping registration rollers 15 for a predetermined time, to form a loop. Subsequently, by rotating the registration rollers 15 in the direction of arrows "e", as shown in FIG. 5, and rotating a feed belt 17 in the direction of arrow "f", as shown in FIG. 6, the sheet is fed to and stopped on a platen 18. Supply of the sheet is thus terminated.
The main body 1 of the copier has an upper cassette 6U, a lower cassette 6B and a deck 4, each for mounting copying paper P. An explanation will now be provided of a case in which the deck 4 is used. A paper-supply roller 31 and first feed rollers 32 in the deck 4 start to rotate immediately after the user has pressed the copy button, and rollers 31 and 32 feed the uppermost sheet of the copying paper P. As shown in FIG. 7, the paper supply roller 31 stops its rotation immediately before the rear end of the sheet passes through the paper supply roller 31. When the front end of the sheet has contacted second feed rollers 33 and a certain degree of loop has been formed in the sheet, the first feed rollers 32 stop rotation, and return to a wait stage.
When the sheet of the original O has stopped at a predetermined position on an original-mount glass 18 by the operation of the ROF 2, exposure is started. A photosensitive drum 34 starts to rotate. Mirrors 36-38 and a halogen lamp 35 project light onto the sheet while moving in the direction of arrow "g" at the same speed as the circumferential speed of the photosensitive drum 34. Toner is supplied from a developing unit 39, and the image on the sheet of the original O is formed on the drum 34. As shown in FIG. 8, the first and second feed rollers 32 and 33, which have been in a waiting state until the front end "h" of the image coincides with the front ends of the second feed rollers 33, start to rotate, and the toner on the drum 34 is transferred to the sheet of the copying paper P. The sheet of the copying paper P having the toner on its surface passes onto a feed belt 40 and through a pair of fixing rollers 41, and is discharged into the stapler/sorter 3 via conveying roller paper-discharge 42 and rollers 43. A bin unit 51 in the stapler/sorter 3, movable up and down in the directions of arrows "i", has a plurality of bins 52 for sorting, and is arranged so that, when m copies each composed of n sheets are to be prepared, the first copy, second copy and m-th copy are discharged into the first bin, second bin and m-th bin, respectively. Accordingly, m copies are prepared by operating only the main body 1 of the copier in the same manner as described above while the sheet of the original O which has previously been supplied to the original mounting glass 18 is not moved, and the m copies are received within the respective bins 52. After the m copies have been prepared, the sheet of the original O is returned to tray 11 in the direction of arrow "j" via a reversal roller 19 and paper-discharge rollers 20, as shown in FIG. 9. The next sheet of an original O is supplied during the discharge operation of the preceeding sheet, and is copied in the main body 1 of the copier. Sheets of the copying paper P having images copies from an original O are stored within the 1st m-th bins of the stapler/sorter 3. Thus, m copies of the mounted original O composed of n sheets are prepared. Subsequently, the sheets having copies images stored in the respective bins are successively stapled by the stapler 5 in sequence from the 1st or m-th bin while the bin unit 51 moves in the direction "i".
Next, an explanation will be provided of a case in which m double-sided copies each composed of n sheets are to be prepared from a single-sided original composed of n pages.
First, a sheet of the original is fed onto the original-mount glass 18 by the ROF 2 as in the case of preparing single-sided copies from a single-sided original. A sheet of the copying paper P is supplied to the drum 34 in the same manner as in the case of single-sided copies. A toner image is then transferred to the copying paper P, and the toner image on the sheet is fixed as the sheet passes through the fixing rollers 41. A movable guide 44 is positioned as shown in FIG. 10 by turning on a solenoid (not shown), and, as a result, the sheet of the copying paper P enters a duplex unit 7 where it is mounted onto an intermediate tray 61, as shown in FIG. 11. When m copies have been prepared, the ROF 2 discharges the original from which the copies have been prepared, as in the same manner as described above, the next original is supplied. The main body 1 of the copier releases a shutter 62 in the intermediate tray 61 by a solenoid (not shown). A paper supply roller 63 is placed on the sheets of the copying paper P in the intermediate tray 61 by a function of a solenoid or the like, starts to rotate, and supplies the uppermost sheet while separating the sheets one by one to a separation roller 64 and a feed roller 65. As shown in FIG. 12, the sheet is fed by rollers 69 and 68, and are pinched by feed rollers 32. Subsequently, a copying operation is performed in the same manner as in the case of supplying a sheet from the deck 4, and the sheet having a copied image is discharged into the stapler/sorter 3.
In the above-described conventional case, if a paper jam occurs while the ROF 2 feeds a sheet of the original O, an already-supplied sheet of the copying paper P, which has not yet had an image transferred to it, is situated before the second feed rollers 33. If the sheet of the copying paper P is stopped at that position and the apparatus tries to use the sheet after a jam recovery, the sheet may itself jam since once the sheet is bent by a guide or the like it has a habit of maintaining the bent state. Hence, it is necessary to discharge the blank sheet of copying paper P immediately after the occurrence of jam.
Accordingly, the prior art has the disadvantage that blank sheets are mixed and stored in a stapler/sorter (or a paper discharge tray), and are stapled in that stage.
When a sorter having fixed bins as shown in FIG. 13 is used, there have been cases wherein blank sheets are discharged onto bins 204, 205, 206 and the like which do not contain sheets having copies images. In the case of a sorter having moving bins, however, the prior art has the disadvantage that one must wait for discharge of blank papers until bins not containing sheets having copied images move up to a discharge port.